Aluminum dust dispersion and flame propagation varying with time in 20 L cylindrical confined chamber were simulated based on computational fluid dynamics theory.The factors influencing flame velocity of aluminum dust were analyzed.Results indicate that when particle size of aluminum dust is in the range of 7-42 μm, the maximum explosion pressure(p_max) decreases with the increasing of particle size.The maximum of p_max and(dp/dt)_max are 0.876 MPa and 120.1 MPa·s^-1, and the minimum are 0.634 MPa and 19.5 MPa·s^-1, which are coincided with the experimental ones in literature with the deviations of p_max and(dp/dt)_max no more than 4.6% and 20%.When the ignition delay time is 60 ms, the flame propagation velocity along the radial direction falls first to a trough, then rises and falls at the end.The maximum and minimum of the velocity are 150.9 cm·s^-1 and 70 cm·s^-1, respectively.